I’ve received a number of questions recently about the scales and gauges | |||||
| Gauge | Name | Scale | Proto- type | Propor- tion | Comments |
| 1.75in (45mm) | 7/8 | 7/8in = 1ft | 24 in | 1:13.7 | Very large trains; for scratchbuilders |
| Fn3 | 15mm = 1ft | 36 in | 1:20.3 | Variant of G, mainly Bachmann | |
| Gm | 45mm = 1m | 1000mm | 1:22.5 | Metre gauge – LGB and others | |
| Hn42 | 1/2in = 1 ft | 42in | 1:24 | Mainly in New Zealand/Australia | |
| 1 | 3/8in = 1ft | 56.5in | 1:32 | Standard gauge – Märklin and others | |
| 1.25in (32mm) | 7/8 | 7/8in = 1ft | 18in | 1:13.7 | For scratchbuilders |
| SM32 | 16mm = 1ft | 24in | 1:19 | Mainly in garden railways | |
| Hn30 | 1/2in = 1 ft | 30in | 1:24 | For scratchbuilders | |
| 1m | 3/8in = 1ft | 1000mm | 1:32 | European metre gauge | |
| 9 Mil | 9mm = 1 ft | 42in | 1:32 | Used mainly in NZ | |
| O (U.K.) | 7mm = 1ft | 56.5in | 1:43.5 | Standard gauge – many mfgrs | |
| O(Europe) | 1435mm | 1:45 | Standard (normal) gauge – many mfgrs | ||
| O (U.S.) | 1/4in = 1ft | 56.5in | 1:48 | Standard gauge – many mfgrs | |
| 7/8in | S | 3/16in = 1ft | 56..5in | 1:64 | Standard gauge |
| 3/4in | 1n2 | 3/8in = 1ft | 24in | 1:32 | For scratchbuilders |
| On3 | 1/4in = 1ft | 36in | 1:48 | Primarily in U.S. | |
| 16.5mm | Gn15 | 13.5mm = 1ft | 15in | 1:22.5 | A few mfgrs |
| Hn18 | 1/2in = 1ft | 18in | 1:24 | A few mfgrs | |
| 1n21 | 3/8in = 1ft | 20-22in | 1:32 | For scratchbuilders | |
| 1/36 | 8.5mm = 1ft | 24in | 1:36 | For scratchbuilders | |
| O16.5 | 7mm = 1ft | ~28in | 1:43.5 | Popular in U.K. | |
| On30 | 1/4in = 1ft | 30in | 1:48 | Popular – Bachmann and others | |
| OO | 4mm = 1ft | 56.5in | 1:76 | U.K. Standard gauge, very popular | |
| HO | 3.5mm = 1ft | 56.5in | 1:87 | Standard gauge, very popular | |
| 14mm | On2, O14 | 7mm = 1ft | 24in | 1:43.5 | Mainly for scratchbuilders – Roy C. Link |
| 12mm | OOn3 | 4mm = 1ft | 36in | 1:76 | U.K. three-foot gauge |
| HOm | 3.5mm = 1 ft | 1000mm | 1:87 | European metre gauge | |
| TT | 2.5mm = 1ft | 1435mm | 1:120 | Standard (normal) gauge | |
| 10.5mm | Sn2 | 3/16in = 1ft | 24in | 1:64 | Mainly in U.S. |
| HOn3 | 3.5mm = 1ft | 36in | 1:87 | Popular in U.S. | |
| 9mm | O9 | 7mm = 1ft | 15in | 1:43.5 | Some U.K. mfgrs – Avalon and others |
| On18 | 1/4in = 1ft | 18in | 1:48 | A few mfgrs | |
| Sn2 | 3/16in = 1ft | 24in | 1:64 | Popular in U.S. | |
| OO9 | 4mm = 1ft | 27in | 1:76 | Popular in U.K. | |
| HOn30 | 3.5mm = 1ft | 30in | 1:87 | Popular, a number of mfgrs | |
| HOe | 3.5mm = 1ft | 650-850mm | 1:87 | Popular in Europe | |
| NZ120 | 2.5mm = 1ft | 42in | 1:120 | New Zealand TTn42 | |
| N | .075in = 1ft | 56.5in | 1:160 | Standard gauge, very popular | |
| 6.5mm | HOn2, HOi | 3.5mm = 1ft | 22-24in,400-650mm | 1:87 | For scratchbuilders |
| Nn3, Nm | .075in = 1ft | 36in, 1m | 1:160 | U.S. three-foot, Europe metre gauge | |
| Z | 56.5in | 1:220 | Standard gauge – Märklin and other | ||